[FFmpeg-devel] [PATCH 09/13] avcodec/svq1dec: clear MMX state after MB decode loop

Ronald S. Bultje rsbultje at gmail.com
Wed Oct 26 00:40:52 EEST 2016


On Tue, Oct 25, 2016 at 5:12 PM, Moritz Barsnick <barsnick at gmx.net> wrote:

> On Tue, Oct 25, 2016 at 14:28:38 +0200, u-9iep at aetey.se wrote:
> > In a perfect world the user might be offered a build time choice:
> > either lose N% of the performance or take the consequences of not
> > following the ABI.
> That was exactly my thought too, assuming it doesn't pollute the code
> even more:
> --disable-fast-simd or --enable-compliant-mmx or something. "auto"
> would detect musl and/or test for the necessity to use emms_c() or
> other measures.

If you don't care about performance, issue a emms upon RET in INIT_MMX
functions (just like we do for vzeroupper in INIT_YMM functions) using
x86inc.asm. Of course, this should be disabled for x86-64 or non-musl

(That doesn't yet deal with inline asm.)


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